A hybrid vehicle is known that has (a) a motor generator disposed in a power transmission path and usable as an electric motor and an electric generator, (b) a direct injection engine capable of ignition start in which fuel is injected into any cylinder and ignited for the start, (c) a friction engagement type engine connecting/disconnecting clutch directly connecting and interrupting the direct injection engine to/from the motor generator. A hybrid vehicle described in Patent Document 1 is an example thereof and, when switching is performed from a motor running mode using only an electric drive portion (corresponding to a motor generator) as a drive force source for running while the engine connecting/disconnecting clutch is interrupted with the direct injection engine stopped to an engine running mode using the direct injection engine as the drive source for running, the direct injection engine is started by the ignition start and, when an engine rotation speed increases and becomes substantially the same as (synchronizes with) a rotation speed of the electric drive portion, the engine connecting/disconnecting clutch is connected to replace a motor torque with an engine torque.
Although the engine can start by itself only through the ignition start in some cases such as when friction of the direct injection engine is small, the engine connecting/disconnecting clutch can be connected at an engine start to give assistance (torque compensation) from the motor generator as needed, and an assist torque can significantly be reduced by the ignition start. As a result, a maximum torque of the motor generator can be reduced to achieve smaller size and lower fuel consumption.